Making Money

美国财政部雕刻和印刷局（BEP）负责为全球最大的经济生产的所有货币负责。从印刷货币每天印刷到其纯粹输出的纸张上，几乎所有方面都是BEP的设计和印刷过程的各个方面都是独特的。许多BEP的质量保证需求也是独一无二的。

与所有打印机一样，BEP必须验证其印刷材料是否清晰准确。

但是，BEP还需要确保在适当的情况下确保有各种安全措施来帮助阻碍伪造，并允许政府占所有银行票据。为了帮助满足这些苛刻的要求，BEP将其几个检验站从人类运营商现货检查货币转换为每项票据的自动视觉检查。

BEP选择了Sherlock Machine Vision软件应用，用于开发三台机器视觉系统：用于印刷板材质量保证的自动检测系统;测量印刷注册一致性注释笔记的自动化;并在新印刷的账单上的质量和安全功能的在线测量。

确保板块质量

In order to reduce or eliminate inconsistencies associated with physical note size and the location of engraved images on the chrome intaglio printing plates on which the currency is printed, the BEP’s Production Engineering group developed a Plate Measurement Device (PMD). The PMD uses state-of-the-art positioning technology and machine vision to automatically measure the layout pattern of the security features on these plates. The engraved artwork and registration marks are gauged before production to verify plate accuracy—which is essential for precise print registration—and afterwards, so that any distortion caused by prolonged intaglio printing is identified.

该团队使用各种先进的现成的光电元件开发了PMD的机器视觉检测系统。集成在主机个人计算机内的帧Grabber捕获来自1k x 1k像素单色相机的图像。使用具有0.5英寸视野的精密镜头，相机达到+/- 0.001英寸的测量公差。除了捕获图像进行分析外，帧抓取器还提供用于监视PMD上的手动开关设置和安全传感器的数字输入/输出（I / O）。操作员通过键盘和鼠标使用自定义的图形界面控制视觉系统，21英寸颜色显示器显示正在检查货币板的实时图像。

因为抛光的镀铬板成形为遵循四板印刷圆筒半径，所以获得质量，高分辨率图像是团队成员面临的主要挑战之一。They solved the problem by using a light emitting diode (LED)-based, dark field illuminator in conjunction with a megapixel camera, making the engraving appear clear and well-defined for the machine vision software’s calipers to perform measurement functions with minimal pre-processing of the image. After the PMD captures all pertinent plate data, analysis is performed using machine vision software and an object oriented program language, and then all data is automatically saved to a network database.

所有完成的纸币都是相同的大小，每张纸32个。虽然在印刷机上的电子上被电子检查，但在纸币编号之前再次，BEP没有可靠的方式来识别由于累积的细微变化而产生的成品纸币具有与许多打印阶段和与之相关的修剪操作的累计微妙变化而发生的。货币生产。如果没有此信息，BEP无法量化其流程能力或衡量纸币质量的改进。

Vision challenges

Therefore, the Production Engineering group developed a vision-based note measurement system that automatically measures and records 27 note registration features (137 data points) on each cut bill. These include substrate size, intaglio print size and position (on both sides) and positions of the seals and serial numbers. Measuring banknotes in reflected light is quite challenging, as the intaglio printing process is somewhat variable by nature, and finding print edges consistently on the fine engraved artwork is very difficult.

基于图像的检查系统被证明是一种成功的方法，并提供足够的灵活性来适应多个纸币设计。每个音符测量站由真空夹具组成，以保持和定位纸币，三种数码相机，微处理器控制的光源，连续漫射照明器（CDI），配备两个帧抓取器的PC和两个机器视觉软件包的CO- 用于图像分析的人。在每张音符精确定位在相机下方后，每个音符的正面和背面的图像被拍摄并转移到帧抓取器。然后通过机器视觉应用分析每个捕获的图像，用于光学字符识别（OCR）和CALiper测量。

该软件的工具还用于解析修剪和打印的变化，并补偿真空表上不正确的音符。使用灰度边缘检测，机器视觉软件应用程序能够在+/- 0.2 mm内精确测量像素和子像素的精度。这是解决方案成功的关键方面，因为纸币上印有许多细线特征小于相机的像素分辨率。

通过持续的质量考虑和越来越需要安全功能来帮助阻碍伪造，BEP的生产工程团队还开发了一种自动检测系统，用于检查每个钞票的半封面，机器可读功能。通过在整个打印的纸张中的精确位置处的面额特定模式应用墨水来创建此功能。

BEP已经使用人类检查员进行了此申请，但每小时只有8,000到10,000张32张纸币，只有一个非常小的纸张被检查，而且比BEP更少的可靠性可以从网上获取，自动化系统。

生产工程集团的检测系统从8位单色系绳头相机开始，可提供更高的灵敏度和低光成像功能。除了从相机捕获图像之外，帧抓取器提供了激活灯条和语音模块的数字I / O功能。这些指标提供了有关每张纸张（印刷和基板区域）的反馈的运营商，因此可以快速地进行任何问题。

系统福利

In each of the three applications for which it has implemented machine vision software solutions, the BEP has benefited from improved quality assurance, better information about its processes—which allows any needed action to be taken quickly—and reduced human inspection costs, along with increased inspection accuracy.

The Production Engineering team is currently making improvements to the existing systems to gain even greater reductions in print variability and to inspect even more sophisticated security features. The group continually makes improvements to its processes for quality assurance and security purposes, and machine vision plays an important role in this regard. The data received from these inspection systems also will be instrumental in implementing future security or design changes.